Wafers, for instance silicon wafers, require a plurality of treatment processes, among them coating processes, for the manufacture of semiconductor elements. As a first step, the polished surface of the wafer must be provided with an adhesion promoter, by the process known as priming, so that a suitable structure can be applied subsequently in a photolithographic process. Furthermore, processes are needed in which the wafer is either cooled down or heated in accordance with a predetermined time curve. All of these processes are done substantially in a clean-room atmosphere and/or in a protective gas atmosphere.
In the aforementioned so-called priming, the wafer is placed, in a largely closed room, on a dish that is filled with an evaporating process medium, namely HMDS (hexamethylenedisilicane). Extreme clean-room conditions must prevail, because the wafer must not become contaminated by even the smallest foreign particle. The process time (priming time) is approximately 4 to 5 minutes, and thus is longer than most of the ensuing process times in the production line, which are on the order of magnitude of only one minute. The cycling time of the intermittently operating system is therefore designed for approximately one minute, and the priming takes place in a kind of buffer apparatus in which a plurality of wafers are located.
Known apparatuses for the priming of wafers are embodied in the form of a tunnel, which is provided with a plurality of treatment stations, for example 5 in number, along its length, or in other words for the treatment of 5 wafers as an example. The wafers are moved in increments through the tunnel, in which the process medium is disposed in an elongated dish, by means of a transport apparatus in such a manner that the aforementioned process time of the production line is attained. The tunnel has an inlet lock and an outlet lock, which can be opened and closed at the cycling rate of this tunnel.
Known apparatuses in which the wafers are cooled down or heated, which is for instance done in a protective gas atmosphere, each have only a single treatment station for a single wafer, so multiple apparatuses are therefore typically provided along the process line. Since once again the process time of this heat treatment apparatus is greater than the average cycling or process time of the production line, these heat treatment apparatuses are located next to the transport apparatus and are alternately loaded.
A disadvantage of the known tunnel-like priming apparatus is its great structural length, and furthermore the fact that the transport apparatus is guided through the processing station, which means that its mechanically movable parts cause abrasion and can contaminate the wafers. Furthermore, because of drafts, the tunnel-like arrangement does not permit uniform distribution of the fog of the evaporated process medium.
The known heat treatment apparatuses have the disadvantage that since they are each intended for only a single wafer, a plurality of them must be provided at a time, so that multiple handling devices for feeding the wafers into and out of the apparatuses must also be provided.